Intermediate housing section for a multi-rotor rotary internal combustion engine and method of manufacture thereof

ABSTRACT

The intermediate housing section for a multi-rotor rotary internal combustion engine comprises two open face housing parts which are secured together with the open faces in abutment. Each of the abutting open face surfaces is formed to have an arcuate surface which in the free or unsecured state abut each other along a tangent line formed by an imaginary plane and the arcuate surface. The abutting arcuate surfaces, when the housing parts are secured together at their peripheries, establish compressive stress forces directed inwardly of the peripheries of the housing parts which forces resist the thermal forces tending to move the housing parts out of abutment.

United States Patent 1191 Jones 1451 Nov. 19, 1974 INTERMEDIATE HOUSING SECTION FOR A MULTI-ROTOR ROTARY INTERNAL COMBUSTION ENGINE AND METHOD OF MANUFACTURE THEREOF I Charles Jones, Hillsdale, NJ.

Curtiss-Wright Corporation, Wood-Ridge, NJ.

Filed: May 11, 1973 Appl. No.: 359,248

Inventor:

Assignee:

us. (:1 418/60, 29/1564 R, 29/446, 29/463, 418/270, 123/8.07 1m. 01. 1323p 1s 90 0 1 1/02, F010 21/00 Field of Search 418/60, 61 A, 279

References Cited UNITED STATES PATENTS 11/1962 Bentele 418/60 Fisher 29/446 FOREIGN PATENTS OR APPLICATIONS 756,392 9/1956 Great Britain 29/449 Primary Examiner--John J. Vrablilt Attorney, Agent, or Firm--A. Frederick 5 7] ABSTRACT The intermediate housing section for a multi-rotor rotary internal combustion engine comprises two open face housing parts which are secured together with the open faces in abutment. Each of the abutting open face surfaces is formed to have an arcuate surface which in the free or unsecured state abut each other along a tangent line formed by an imaginary plane and the arcuate surface. The abutting arcuate surfaces,

when the housing parts are secured together at their peripheries, establish compressive stress forces directed inwardly of the peripheries of the housing parts 4 which forces resist the thermal forces tending to move the housing parts out of abutment.

8 Claims, 4 Drawing Figures INTERMEDIATE HOUSING SECTION FOR A MULTI-ROTOR ROTARY INTERNAL COMBUSTION ENGINE AND METHOD OF MANUFACTURE THEREOF This invention relates to intermediate housing sections for multi-rotor rotary internal combustion engines and, more particularly, to a two-piece or split intermediate housing and a method of fabrication thereof.

In multi-rotor internal combustion rotary engines ofthe Wankel type, such as disclosed in the US. Pats. to Bentele No. 3,062,435; Jones, No. 3,193,187; Jones, No. 3,240,423; Takebayashi, No. 3,279,279 and Zimmerman, No. 3,302,623, intermediate housing sections are provided to define with other housing sections, such as a trochoid housing section and end wall sections, side-by-side cavities within which the rotors are supported for rotation. In some multi-rotor rotary internal combustion engine designs, ease of assembly and disassembly is promoted by providing intermediate housing sections that are constructed of two housing parts suitably secured together by removable fastening means. It has been found that such two-piece intermediate housing sections wherein the two housing parts are secured together at their peripheries do not have the same desirable structural strength. as the unitary cast or two-piece bonded intermediate housing'section. The requisite structural strength is necessary to resist the forces produced by the thermal distortions to which the intermediate housing sections are subjected. This non-uniform heating of the housing of an internal combustion rotary engine is fully disclosed in the US. Pats.

to Jones No. 3,196,850, No. 3,302,622 and No. 3,318,515. In intermediate housing sections of the type having two housing parts bolted together at the peripheries, the thermal distortion of the housing parts results in openings between the abutting surfaces, higher oil consumption, fluid leakage and excessive wear of rotor seals and components.

Accordingly, it is an object of this invention to provide in a multi-rotor internal combustion rotary engine an intermediate housing section, having two housing parts, which has the structural strength to resist distortion due to the non-uniform thermal stress to which the intermediate housing section is subjected.

Another object of the present invention is to provide, for a multi-rotor internal combustion rotary engine, an

intermediate housing section, having two housing parts,

which has a desired structural strength even though secured together only at the peripheries of the housing parts.

A further object of this invention is to provide a method of fabricating an intermediate housing section of two housing parts for a multi-rotor internal combustion rotary engine. which method is relatively simple and inexpensive. r A feature of this invention is the forming of the abutting surfaces of each of the two housing parts so that the clamping of the housing parts together produces compressive stresses in each housing part acting along the plane of the interface or abutment to maintain the abutting surfaces in continuous contact during all operating conditions of the engine.

SUMMARY Accordingly, the present invention contemplates a novel intermediate housing section for a multi-rotor,

rotary internal combustion engine: which housing section comprises two abutting housing parts secured together. Each of the housing parts may be open-faced castings or forgings with the surfaces at the open-face corresponding to or matching the surfaces at the openface of the other housing part so that, when assembled, the surfaces abut each other. In accordance with this invention, the abutting surfaces of each of the housing parts are so formed that prior to being secured together the surfaces lie in a'portion of a cylindrical surface. The line of tangency between the cylindrical surface and an imaginary plane extending parallel with the opposite closed-faces of the housing parts passes substantially through the center of each of the housing parts. In fabrication, the housing parts are arranged in abutment along the aforesaid line of tangency and are clamped, at their peripheries, by suitable means, such as a plurality of spaced bolts, to draw the matching surfaces into abutment and thus, produce compressive stresses in each housing part acting along the plane of abutment to maintain the abutting surfaces in continuous contact. The radius of the curvature of thecylindrical surface is selected to be of a magnitude greater than distortion of an unassembled housing part when it is subjected to the same thermal stresses it would encounter in an operating engine. This feature insures that under engine operating conditions the compressive stresses will always be sufficient to insure firm abutment of the housing parts. For example, the aforesaid radius in a housing having a tangency line of 12 inches in length will produce at the opposite peripheral portions a housing part width of 0.005 of an inch smaller than the housing part width at the center of such cylindrical surface, before final machining of the opposed wear surfaces to a parallel condition after the halves have been clamped together.

In a preferred aspect of this invention, the aforesaid tangency line extends through the area of greatest heat flux for more uniform distribution of thermal distortion within each of the housing parts.

The method of fabrication of the intermediate housing section of this invention comprises casting or forging two open-face housing parts and then machining each of the housing part surfaces at the open-face so that they lie in a portion of a cylindrical surface. Each of the cylindrical surfaces is formed so that a tangency BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the.

following description when considered in connection with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an intermediate housing section according to this invention prior to assembly of the housing parts;

FIG. 2 is a cross-sectional view similar to FIG. 1 showing the intermediate housing section after assemy;

FIG. 3 is a diagrammatic drawing showing the compressive stresses acting on the housing parts after assembly as shown in FIG. 2; and

FIG. 4 is a schematic drawing illustrating the variation in degree of heat flux to which the intermediate housing section is subjected during operation of multirotor, internal combustion rotary engine of the Wankel type.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION Now referring to the drawings and more specifically to FIGS. 1 and 2, the reference number generally designates the intermediate housing section according to this invention, which housing section forms part of the housing of a multi-rotor rotary mechanism of the Wankel type, such as disclosed in US. Pats. to Bentele No. 3,062,435; Jones No. 3,193,187; Jones, No. 3,240,423; Takebayashi, No. 3,279,279; and Zimmerman, No. 3,302,623. While intermediate housing section 10 will be described as having particular application to internal combustion rotary engines, it is to be understood that the intermediate housing section has application to other types of multi-rotor, rotary mechanisms of the Wankel type, such as expander engines, compressors and pumps, without departure from the scope and spirit of this invention.

As shown in FIGS. 1 and 2, intermediate housing section 10 comprises two housing parts 12 and 14 which are secured together by a plurality of spaced bolts 16 (only one of which is shown) disposed in peripheral portions 18 of the housing parts. The two housing parts 12 and 14 may also be secured together by other suitable clamping means such as tie bolts (not shown) which also extend through other housing components (not shown).

As illustrated in FIG. 4, intermediate housing section 10, as well as other housing components (not shown) are subjected to non-uniform heating and variation in heat flux which is particularly severe in an internal combustion engine application, the heat flux being shown by the broken line and indicated by the proportion Q/A. It can be seen therein that the greatest heat flux is produced in the region of combustion and expansion which region is located by reference to the intake and exhaust ports 20 and 22 and spark plug 24. This heat flux imposes forces tending to distort and cause separation of housing parts 12 and 14 in :spiteof the clamping at the peripheries of the housing parts. To provide intermediate housing section 10 with the structural strength to resist thermal distortion, the intermediate housing section is constructed as hereinafter fully set forth.

As best shown in FIG. 1, each housing part 12 and 14, is formed by casting or forging to provide an openface side 26 and an opposite closed-face side 28. The matching surfaces formingopen-face side 26 of each housing part 12 and 14 are formed as by machining or the like so as to lie in a partial cylindrical surface. The curvature is so located that a tangency line (denoted in FIG. 4 as A-A) between the cylindrical surface and an imaginary plane extends substantially through the center of the associated housing part 12 or 14 and, preferably as shown in FIG. 4, to substantially bisect the heat flux pattern Q/A. The radius of curvature R of the cylindrical open-face 26 is selected to be of a magnitude greater than the calculated distortion of an unassembled housing part 12 or 14 when it is subjected to the same thermal stresses (heat flux Q/A) it would encounter as part of an operating engine. This radius of curvature in an intermediate housing part having a dimension A of 12 inches (see FIG. 1) may result in a width B at the opposite peripheral portions 18 which is 0.005 inches less than the width at C, before final machining of the closed-face sides 28 as hereinafter discussed. As is schematically illustrated in FIG. 3, when bolts 16 are turned to draw housing parts 12 and 14 in tight abutment along their respective curved open-face side 26, such clamping force F sets up or produces in each of the housing parts 12 and 14 compressive stresses (represented by the arrows C) which act to maintain housing part 12 and 14 in tight abutment even when subjected to the thermal stresses produced by heat flux Q/A.

The fabrication of intermediate housing section 10 according to this invention, comprises forming housing parts 12 and 14 by forging or casting to produce the open-face side 26. Each of the open-face sides 26 are machined to the desired predetermined curvature. Thereafter, the open-face sides 26 of each housing part 12 and 14 are brought together in abutment along the tangency line A--A and then clamped together at their peripheries 18 so that all of the surfaces of open-face sides 26 are brought into contact. The closed-face sides 28 are then machined flat to produce a wear face for the rotors which are to be supported for rotation adjacent opposite sides of intermediate housing section 10. Thereafter a fixed timing gear 30 is secured to intermediate housing section in any suitable manner. One such means may be the split cone collar disclosed in the US. Pat. to Jones et al., No. 3,193,187 or the castellated ring disclosed in the Jones et al US. Pat. No., 3,694,l 13.

While the intermediate housing section 10 is shown as an air-cooled assembly having fins 32 for improved heat transfer, intermediate housing section 10 may be constructed to provide liquid cooling passages therethrough. Accordingly, the present invention is not limited to air-cooled rotary mechanisms.

It is believed now readily apparent that the present invention provides an improved two-piece intermediate housing section for a multi-rotor rotary mechanism and a method of manufacture thereof, which provide a housing section capable of resisting thermal distortion even though the two parts thereof are clamped together only at the peripheries thereof. It is a two-piece intermediate housing section which has compressive stresses imposed therein which act counter to the thermal stress forces tending to separate the two parts of the housing section and thus prevent such separation.

Although but one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

What is claimed is:

1. An intermediate housing section for a multi-rotor rotary mechanism which defines with other housing 3,849,035 sections spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the intermediate housing section comprising:

a. a first housing part having integral inner and outer 1 peripheral portions; 5

b a second housing part having integral inner and outer peripheral portions;

c. said first and second housing parts each having a matching surface portion extending from and forming a part of the inner and outer peripheral portions and an opposite substantially flat surface portion;

extending substantially parallel to the wear surface portion and normal to the crankshaft axis and also lies in an imaginary plane projecting substantially through the center axis of the associated housing part and substantially bisecting the region of highest heat flux when the mechanism is in operation.

3. The apparatus ,of claim 2 wherein said difference in the dimension of the housing part at the tangency line and at the peripheral portion is about 0.005 inches for a tangency line of 12 inches.

4. The apparatus of claim 2 wherein the securing means is a plurality of spaced bolts.

5. The method of fabricating a two-piece intermediate housing section for a multi-rotor rotary mechanism which defines with other housing sections of the mechanism spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the method comprising:

d. securing means disposed at the respective outer peripheral portions of the first and second housing parts to clamp said first and second housing parts in abutment along their respective matching surface portions; and

e. each of said matching surface portions having a partial cylindrical configuration such that the maximum extent of the curvature thereof lies substana. forming each of a first and second housing part so tially in an imaginary plane extending through the as to produce an open-face casting; axis of the crankshaft and substantially bisecting b. forming the open-face" portion of each of said the region of highest heat flux and so that, upon the first and second housing parts to have a partial cyhousing parts being clamped together, compressive lindrical convex surface so formed that atangency stresses are created in each of said first and second line between the cylindrical surfaces lies in an housing parts which act to maintain the matching imaginary plane extending substantially parallel to surface portions in continuous abutment at their the opposite face of the associated housing part respective integral inner and outer peripheral porand also lies in an imaginary plane projecting subtions. stantially through the center axis of the associated 2. An intermediate housing section for a multi-rotor housing part and substantially bisecting the region rotary mechanism which defines with other housing sections spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the inc. termediate housing section comprising:

of highest heat flux when the mechanism is in operation;

bringing the first and second housing parts into abutment along their respect tangency lines; and

a. a first housing part; d. clamping the first and second housing parts tob. a second housing part; gether at their peripheral portions to force the c. said first and second housing parts each having a open-face portions of the respective first and matching surface portion and an opposite substansecond housing parts in full abutment. tially flat wear face portion adjacent said rotors; 6. The method of claim 5 wherein said cylindrical d. securing means disposed at the peripheral portions convex surface is formed by machining.

of said first and second housing parts to connect 7. The method of claim 5 wherein the step of securthe latter housing parts together with their respecing a fixed timing gear follows clamping of the first and tive matching surface portions in abutment against second housing parts together. each other; and 8. The method of claim 5 wherein the face portion of e. each of the matching surface portions prior to seeach of said first and second housing parts opposite curing the first and second housing parts together have a convex partial cylindrical surface configurafrom the open-face portion is machined substantially flat and parallel to each other after the first and second tion so formed that a tangency line between said housing parts are clamped together. matching surface portion lies in an imaginary plane 

1. An intermediate housing section for a multi-rotor rotary mechanism which defines with other housing sections spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the intermediate housing section comprising: a. a first housing part having integral inner and outer peripheral portions; b. a second housing part having integral inner and outer peripheral portions; c. said first and second housing parts each having a matching surface portion extending from and forming a part of the inner and outer peripheral portions and an opposite substantially flat surface portion; d. securing means disposed at the respective outer peripheral portions of the first and second housing parts to clamp said first and second housing parts in abutment along their respective matching surface portions; and e. each of said matching surface portions having a partial cylindrical configuration such that the maximum extent of the curvature thereof lies substantially in an imaginary plane extending through the axis of the crankshaft and substantially bisecting the region of highest heat flux and so that, upon the housing parts being clamped together, compressive stresses are created in each of said first and second housing parts which act to maintain the matching surface portions in continuous abutment at their respective integral inner and Outer peripheral portions.
 2. An intermediate housing section for a multi-rotor rotary mechanism which defines with other housing sections spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the intermediate housing section comprising: a. a first housing part; b. a second housing part; c. said first and second housing parts each having a matching surface portion and an opposite substantially flat wear face portion adjacent said rotors; d. securing means disposed at the peripheral portions of said first and second housing parts to connect the latter housing parts together with their respective matching surface portions in abutment against each other; and e. each of the matching surface portions prior to securing the first and second housing parts together have a convex partial cylindrical surface configuration so formed that a tangency line between said matching surface portion lies in an imaginary plane extending substantially parallel to the wear surface portion and normal to the crankshaft axis and also lies in an imaginary plane projecting substantially through the center axis of the associated housing part and substantially bisecting the region of highest heat flux when the mechanism is in operation.
 3. The apparatus of claim 2 wherein said difference in the dimension of the housing part at the tangency line and at the peripheral portion is about 0.005 inches for a tangency line of 12 inches.
 4. The apparatus of claim 2 wherein the securing means is a plurality of spaced bolts.
 5. The method of fabricating a two-piece intermediate housing section for a multi-rotor rotary mechanism which defines with other housing sections of the mechanism spaced adjacent rotor cavities within which rotors are supported for rotation on a crankshaft, the method comprising: a. forming each of a first and second housing part so as to produce an ''''open-face'''' casting; b. forming the ''''open-face'''' portion of each of said first and second housing parts to have a partial cylindrical convex surface so formed that a tangency line between the cylindrical surfaces lies in an imaginary plane extending substantially parallel to the opposite face of the associated housing part and also lies in an imaginary plane projecting substantially through the center axis of the associated housing part and substantially bisecting the region of highest heat flux when the mechanism is in operation; c. bringing the first and second housing parts into abutment along their respect tangency lines; and d. clamping the first and second housing parts together at their peripheral portions to force the ''''open-face'''' portions of the respective first and second housing parts in full abutment.
 6. The method of claim 5 wherein said cylindrical convex surface is formed by machining.
 7. The method of claim 5 wherein the step of securing a fixed timing gear follows clamping of the first and second housing parts together.
 8. The method of claim 5 wherein the face portion of each of said first and second housing parts opposite from the ''''open-face'''' portion is machined substantially flat and parallel to each other after the first and second housing parts are clamped together. 